JPH0196602A - Manufacture of hollow optical waveguide - Google Patents

Abstract

PURPOSE:To reduce the loss and increase the transmission power capacity by forming a specific dielectric thin film and an external metallic layer, and then drawing a base material and forming a hollow pipe. CONSTITUTION:An internal metallic layer 4 is formed on the base material 1 to form a specular surface with high smoothness as the surface of the base material, and the dielectric thin film 2 is formed thereupon while having larger adhesive strength than that between the base material 1 and internal metallic layer. Then, the external metallic layer 5 which is thick enough to have mechanical strength and flexibility is formed outside the dielectric thin film 2 and then the base material 1 is drawn having the internal metallic layer 4 stuck to form the hollow pipe. Namely, the surface of the base material with high smoothness is formed as the base material surface not by providing the dielectric thin film 2 directly on the base material 1, but by interposing the internal metallic layer 4. Consequently, the transmission loss is reduced and the power transmission capacity is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a hollow optical waveguide, particularly a flexible metal hollow optical waveguide having a dielectric inside.

[Conventional technology] CO2 lasers, which can obtain high output with high efficiency, have begun to be used mainly for processing and medical purposes, and their applications are also expanding to isotope separation, gas*a measurement, etc. .

However, compared to YAG lasers that can use low-loss and flexible silica-based optical fibers, CO2 lasers with a wavelength of 10.6 Jal
In the case of two lasers, the unavailability of low-loss flexible waveguides has been a major obstacle in its application, and it has been a long time since its realization.

Currently, the most promising candidate is Ge, which has low loss in the 1G and 6Jll wavelength range, for the inner surface of metal pipes.

By coating with a dielectric material such as znse, the reflectance of the inner surface of the metal pipe is increased, creating a hollow pipe! This is a hollow metal waveguide with a dielectric interior that confines and transmits laser energy.

The yJ manufacturing method of this waveguide will be explained below with reference to FIG.

The material of the base pipe 1 is M or polyimide. In the case of M, the outer surface must be mirror-finished using, for example, diamond paste (FIG. 2(a)). On the outer surface of the base material pipe 1, a layer of Ge with a thickness of about 0.5 μs or Zn5e with a thickness of about 0.8 Ia is formed by high frequency magnetron sputtering (FIG. 2(b)). On the outer surface of this dielectric thin film 2, there is a metal thin film 3 such as A (1° Cu, edges, etc.).
form. The thickness is equal to or greater than the skin depth at a wavelength of 10.6, and is sufficient if it is approximately 300 Å or greater (FIG. 2(C)). Next, the surface of this metal thin film 3 is coated with N by bright plating in a Watt bath or a sulfamic acid bath, for example.
One layer 4 is formed. Its thickness is determined from mechanical strength, and is approximately 100 to 200 JJIR (Fig. 2(d)). Finally, the base material pipe 1 is removed by etching to produce a dielectric-internal metal hollow waveguide (Fig. 2(e)).
. As the etching solution, a NaOH solution with a concentration of about 10% is used in the case of M, and a mixed solution of hydrazine and ethylenediamine is used in the case of polyimide.

[Problems to be Solved by the Invention] With the prior art described above, it is difficult to obtain a mirror-like surface of the base material with a sufficiently high degree of smoothness, and the unevenness of the base material surface remains as it is on the inner wall surface of the hollow waveguide. As a result, mode conversion to higher-order modes with large losses occurs within the waveguide.
As a result, the transmission loss of the waveguide becomes large.

For example, in the case of an M vibe made using the pulling method, pulling 1
& Even small dust particles mixed in the oil can easily cause deep scratches in the axial direction. Furthermore, since M is soft, it is difficult to polish the surface to a mirror finish.

On the other hand, when polyimide is used as the base material, the surface smoothness is superior to that of the M vibe, but the presence of bits and voids on the surface still causes an increase in loss. Furthermore, since the base material is removed by etching in the final step, it cannot be reused and treatment of etching waste liquid is required, which is problematic in terms of follow-on flow. Further inner diameter 1.5#III
It is extremely difficult to completely remove the base material from the inner wall of the waveguide, and the slight amount of residue present on the inner wall of the waveguide also causes an increase in loss.

The purpose of the present invention is to eliminate the drawbacks of the prior art mentioned above, and to provide a hollow light guide which has a highly mirror-finished surface of the base material pipe, has low loss, has a large transmission power capacity, and can reuse the base material. An object of the present invention is to provide a method for manufacturing a wave path.

[Means for Solving the Problems] The method for manufacturing a hollow optical waveguide of the present invention includes providing an internal metal layer on a base material to form a mirror surface with high flat'/n marks on the surface of the base material,
A dielectric thin film is provided thereon so that the adhesion force is weaker than that between the base material and the inner gold layer.

A thick outer metal layer with mechanical strength and flexibility is formed on the outside of this dielectric film, and the base material is pulled out with the inner metal layer still attached to form a hollow tube. It was designed to do so.

[Function] By interposing the internal metal layer instead of directly providing the dielectric 749 film on the base material, the surface of the base material can be formed into a smooth and highly mirrored surface, thereby reducing waveguide loss.

Furthermore, if the adhesion between the dielectric thin film and the internal metal layer is weaker than that between the base material and the internal metal layer, when the base material is pulled out, the internal metal layer will not be left behind but will come out adhering to the base material.

If the base material is pulled out instead of being removed by chemical etching, it becomes possible to reuse the base material.

[Example] Hereinafter, an example of the present invention will be described with reference to FIG.

The base material 1 having a circular cross section is, for example, M. The surface is simply roughly polished using a commercially available metal abrasive or the like (FIG. 1(a)). Next, using this M base material 1 as a cathode, Ni is coated with bright Ni plating.
A plating layer 5 is formed (FIG. 1(b)).

Its thickness is 2~! zmPi! Using a Watts bath, the pH was 4.0, the bath temperature was 43°, and the Ti flow density was 4 O.
It is obtained by plating for 5 to 12 minutes under A/d conditions.

The leveling effect of the brightener greatly improves the smoothness of the base material. Furthermore, the surface is polished using diamond paste to make it mirror-like. Since Ml is harder than M, it is easier to obtain a mirror surface and submicron surface roughness can be achieved.

A dielectric thin film 2 having a low loss at a wavelength of 10.6 m is formed on the outer surface of the old plating layer 5 by high frequency magnetron sputtering to a thickness determined by the refractive index of the material (FIG. 1(C)).

The thickness of this dielectric thin film 2 is approximately 0.5p in the case of GO.

In the case of 2nSe, it is about 0.8-, and its design theory is described by Miyagi et al.
etric-Coated Circular Met
allic Waveguides for In-f
raredTransmission, ”I[EE
, J. of Lightwave Tech.

vol, LT-2AI) ril 1984). Kono dielectric 'a! I! Ao on the outer surface of J2
, CO, Au, etc., having a wavelength of 10.6- and a large value of the imaginary part of the complex refractive index, a metal thin film 3 is formed by high-frequency magnetron sputtering. (Figure 1(d)). The thickness may be approximately 100A to 5000A as long as it is equal to or greater than the skin depth at a wavelength of 10.6I11. This metal thin film 3
An old plating layer 4 is formed on the outer surface of the substrate using a Watt bath or a sulfamic acid bath (FIG. 1(e)). This Xi
Since the plating H4 requires flexibility, it is desirable to reduce the ω of the brightener compared to the Ni plating layer 5 formed on the base material 1. Next is Ni Meriki! The base material 1 is pulled out with the rI5 still attached to the base material 1 (FIG. 1(f)). Dielectric thin film 2 and N1 plating applied by sputtering!
The adhesion force between II5 is the base material 1 attached by plating and the Ni
Plating! This method is possible because the adhesion force is weaker than that between 45 and 45. Furthermore, lowering the ambient temperature is also an effective method when drawing out the material. The base material 1 pulled out in this manner can be reused by being packed and polished again as described above.

As mentioned above, according to this example, the smoothness of the base material surface was greatly improved by bright plating and diamond paste 1ffi, so it was possible to reduce the loss of the waveguide, and furthermore, it could be used as an alternative method to chemical etching of the base material. By using the drawing method, it is possible to reuse the base material, improve durability, and eliminate increased loss due to edging residue.

In the above embodiment, electrolytic X was used to form the Ni plating layer 5.
Although the i-plating method was used, electroless Xi-plating is also possible. Further, structurally, even if the metal thin film 3 is omitted, a waveguide with sufficiently low loss can be realized.

[Effect of the invention] According to the present invention, there are the following effects.

Since the surface roughness of the inner wall of the hollow optical waveguide has been greatly improved, transmission loss can be significantly reduced and power transmission capacity can be increased.

(2) Furthermore, since the base material can be reused and there is no need to treat waste liquid from etching, the process can be simplified and is extremely economical.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of the manufacturing process for a hollow optical waveguide according to the present invention, and FIG. 2 is an explanatory diagram showing an example of the manufacturing process for a conventional hollow optical waveguide. In the figure, 1 is the base material, 2 is the dielectric WJll, 4 is the Ni plating layer (inner metal layer), and 5 is the Ni plating layer (outer metal layer).
It is.

Claims (2)

[Claims] (1) An internal metal layer is provided on the base material to form a mirror surface with high smoothness, and a dielectric thin film is provided on top of it so that the adhesion force is weaker than between the base material and the internal metal layer. , furthermore, after forming a thick outer metal layer with mechanical strength and flexibility on the outside thereof, the base material is pulled out with the inner metal layer still attached to form a hollow tube. A method for manufacturing a hollow optical waveguide. (2) The method for manufacturing a hollow optical waveguide according to claim 1, wherein the internal metal layer on the surface of the base material is formed by a bright plating method.